1. Field of the Invention
The invention relates to the fields of chemistry and biology. More specifically, the invention relates to capture of CO2 from a gas phase and subsequent delivery of the carbon to a medium promoting the growth of photoautotrophic organisms and the production of biofuels therefrom.
2. Description of the Related Art
Global warming is largely attributed to an increase in atmospheric CO2, which results from the combustion of fossil fuels. In order to combat this phenomena, a great deal effort focuses on removal of CO2 from the atmosphere, industrial sources and gas processing sources via various capture methodologies.
US Patent Application Publication No. 2008/0138265 [leading to U.S. Pat. No. 7,699,909] discloses methods and systems for extracting, capturing, reducing, storing, sequestering, or disposing of carbon dioxide (CO2), particularly from the air. US Patent Application Publication No. 2008/0087165 to Wright et al. (leading to U.S. Pat. No. 7,708,806 and in the family of PCT Application No. PCT/US2007/080229) discloses the extraction of CO2 from air using conventional extraction methods or by using a humidity swing or electro dialysis method, and the subsequent delivery of CO2 to a greenhouse or algal culture using a porous membrane. US Patent Application Publication No. 2009/0232861 to Wright et al. discloses the extraction of CO2 from a fluid stream and the delivery of CO2 to controlled environments using a porous membrane, where the CO2 is utilized by a secondary process. US Patent Application Publication No. 2009/0120288 discloses the removal of carbon dioxide, from ambient air various sorbent technologies. In addition, there are numerous publications and patents describing capture and sourcing of CO2 from anthropogenic streams (e.g., flue gas from coal fired power plants).
In adsorption-based CO2 capture, the regeneration of the loaded adsorbent poses several potential hurdles. Of primary concern is the amount of energy required, i.e. steam generation, and chemical stability of the sorbent within the stripping environment, especially for amine-functionalized sorbents in a steam stripping environment. In addition the delivery of CO2 to algal photobioreactors must also overcome several technical challenges including the need to deliver pure CO2 to the reactor and minimize the headspace volume that nitrogen and other inert gases occupy in the photobioreactor, the solubility limit of CO2 in the aqueous phase if delivery through the water stream is preferred, the energy penalties incurred with transport of large volumes of gas to many modular reactors if gas phase delivery is selected and the need to avoid alteration of the ionic content of the photoautotrophic culture medium, which could compromise the health and productivity of the photoautotrophs. None of the cited references addresses these concerns. However, in the present invention we present a process invention for integrated sorbent regeneration and CO2 delivery that addresses these technical concerns.